Field of the Invention
The present invention relates to an inorganic film-forming composition for multilayer resist processes, and a pattern-forming method.
Discussion of the Background
Miniaturization of semiconductor devices and the like has been accompanied by the progress of a reduction in processing size by utilizing a multilayer resist process in order to achieve a higher degree of integration. In the multilayer resist process, an inorganic film is provided on a substrate using an inorganic film-forming composition, and then a resist pattern is formed on the inorganic film using an organic material that differs in etching rate from the inorganic film. Next, the resist pattern is transferred to the inorganic film by dry-etching, and further dry-etching is executed to transfer the pattern to the substrate, whereby a desired patterned substrate is obtained (see Japanese Unexamined Patent Application, Publication Nos. 2001-284209, 2010-85912, and 2008-39811). Recently, in addition to composition containing a silicon-containing compound, a composition has been investigated as the inorganic film-forming composition, which contains a metal-containing compound and can exhibit superior etching selectivity with respect to a silicon dioxide film provided adjacent to the inorganic film and also with respect to a resist underlayer film which is an organic film (see Japanese Unexamined Patent Application (Translation of PCT Application), Publication No. 2005-537502).
Such an inorganic film-forming composition is required to meet the following various characteristics. First, it is required that in forming a pattern, a coating film left after drying the composition can be removed through dissolution in a cleaning solvent used in an edge-and-back rinsing for cleaning the edge and the back face of the substrate. Moreover, the resulting inorganic film is required not only to be superior in the etching selectivity mentioned above, but also to enable a favorable shape of a resist pattern to be formed on the inorganic film. In addition, in order to achieve a sufficient antireflection effect in the multilayer resist process, it is reportedly preferred that the extinction coefficient of the inorganic film falls within a range of about 0.1 to about 0.5, and accordingly, the inorganic film-forming composition is also required to provide an inorganic film having such an extinction coefficient.